Data storage systems often include multiple devices that serve different purposes. For example, a data storage system may include a backing device (such as a disk drive) that provides relatively slow and inexpensive long-term storage for application data. In this example, the data storage system may also include a cache device (such as a solid-state drive) that provides relatively fast and expensive short-term storage for the application data.
In order to function properly, the data storage system may need to maintain a certain level of consistency across the application data stored in the backing device and the cache device. For example, when an application issues a write operation, the data storage system may perform the write operation on the cache device and then propagate the write operation to the backing device in order to synchronize the application data stored in the backing device and the cache device. By synchronizing the application data stored in the backing device and the cache device, the data storage system may ensure that the application does not experience downtime or input/output errors resulting from inconsistencies between the backing store and the cache device.
Unfortunately, in the event that the data storage system is unable to successfully perform the write operation on the backing store (due, e.g., to one or more system failures), the data storage system may be unable to synchronize the application data stored in the backing store and the cache device. As a result, the application data may develop inconsistencies that ultimately lead to application downtime or input/output errors. What is needed, therefore, are systems and methods for eliminating inconsistencies between backing devices and cache devices in order to avoid application downtime and input/output errors resulting from failed write operations.